[Net] MultiplayerReplicator with initial state.

Move the former "spawnables" functions to a dedicated
MultiplayerReplicator class.
Support custom overrides in replicator.
Spawn/despawn messages can now contain a state.
The state can be automatically encoded/decoded by passing the desired
object properties to `spawnable_config`.
You can use script properties to optimize the state representation.
2 Callables can be also specified to completely override the default
implementation for sending and receiving the spawn/despawn event.
(9 bytes overhead, and there's room for improvement here).
When using a custom implementation `spawn` and `despawn` can be called
with any Object, `send_spawn`/`send_despawn` can receive any Variant as
a state, and the path is not required.

Two new functions, `spawn` and `despawn`, convey the implementation
independent method for requesting a spawn/despawn of an Object, while
`send_spawn` and `send_despawn` represent the more low-level send event
for a Variant to be used by the custom implementations.

1 files changed, 1 insertions, 1 deletions

diff --git a/scene/main/node.h b/scene/main/node.h
index 9997f4e055..6616524866 100644
--- a/scene/main/node.h
+++ b/scene/main/node.h
@@ -202,7 +202,7 @@ protected:
 	static String _get_name_num_separator();
 
 	friend class SceneState;
-	friend class MultiplayerAPI;
+	friend class MultiplayerReplicator;
 
 	void _add_child_nocheck(Node *p_child, const StringName &p_name);
 	void _set_owner_nocheck(Node *p_owner);